1. Field of the Invention
The invention relates to a winding apparatus in which the winding wire is fed from a feed spool to a core or jig to be provided with a winding, and in which a tensioning device is arranged between the feed spool and the core or jig, the apparatus further including means for braking a wire. The wire tensioning device is formed by two flat plates which are arranged at some distance from each other and which are maintained at that distance by two side strips on the sides of the plates, the gap formed between the plates being closed on one side by a closing member comprising an inlet opening and an outlet opening for the wire and also an inlet for compressed gas.
2. Description of the Prior Art
Winding apparatus of the kind described above are known from French Patent Specification No. 2,185,282.
Such apparatus can be used, for example, for depositing windings on rotors of electric motors having a rectangular or oval section. They can also be used for providing windings on toroidal cores of deflection coils for cathode ray tubes which also have an irregular section. Furthermore, using these machines saddle-shaped deflection coils can be wound on an irregular form.
Due to the asymmetrical shape of the core of the jig, the wire consumption during winding will vary as the angle of rotation varies; that is, the speed at which the wire is deposited on the core or the jig is subject to variation.
If the center of rotation of the winding jig or of the wire guide is situated outside the core to be provided with a winding, the winding wire must be periodically pulled back to avoid loose deposition of the wire.
As a result, variations in wire tension frequently occur, and these variations cause loose deposition or breakage of the wire at high winding speeds. Moreover, fluctuating wire tension causes irregular distribution of the turns, which is particularly undesirable in the case of deflection coils for television sets.
In order to reduce fluctuations in the wire tension, it is known to arrange a wire braking and tensioning device between the feed spool and the core or jig. Such a device should be able to take back a quantity of wire as quickly as possible during winding, so that the wire always remains taut; also, wire tension must be maintained as constant as possible, without any high tension peaks.
In a known device in accordance with the French Patent Specification No. 2,185,282 a supply of compressed air causes a pressure difference to arise across a length of the wire in a gap. This pressure differential exerts a constant force per unit length of wire, resulting in a given wire tension. Under the influence of the compressed air, the wire forms a loop which becomes smaller or larger as the wire accelerates or decelerates. The adaptation of the loop is very quick, because only the mass of the wire need be accelerated. However, the wire tension varies with the size of the loop.
In order to ensure that the wire loop in the tensioning device does not become too small or too large, this known device requires feedback to a separate wire braking device. Obviously, a separate wire brake of this kind makes the device expensive.